Filters are often used in airflow paths in order to remove particulate matter from air. Such airflow paths may include those in vacuum cleaners or furnaces, for example. Filters may be made from a variety of filter materials, which may be used alone or in combination.
Previously, vacuum cleaners used filter bags that were typically constructed from paper. A disadvantage of filter bags is that they could rip or puncture, thereby releasing too much dirt into a room that is being cleaned. Bags could also be difficult to replace and could result in the release of dirt from the bag when a used bag was removed from the vacuum cleaner.
Commencing in about the 1980's, vacuum cleaners were commercialized which used cyclones as the primary filtration means. Currently, many commercial vacuum cleaners use at least one cyclone for dirt filtration. An advantage of the use of cyclones is that the user does not have to change a bag. Instead, the user has to typically remove the cyclonic cleaning stage from the vacuum cleaner, open the cyclonic cleaning stage if needed, and empty the dirt container or containers therein. A disadvantage with such a design is that the dirt collected in the dirt container must be poured or dumped out, resulting in the release of fine dirt into the air.